With particular respect to glass block wall construction, a number of different types of construction systems are employed, each of which have their own associated advantages and disadvantages due to the special and somewhat unique characteristics of glass blocks.
One of the features of glass block construction which is making it become increasingly popular, is its high aesthetic appeal. This is enhanced by the use of modular blocks of substantially identical size and shape which are bonded in a rectangular matrix as opposed to an offset bond, the latter being preferred for brickwork in order to maintain the strength thereof. Subsequently, the bonding of glass blocks in a rectangular matrix generally requires interstitial reinforcement between the blocks to maintain the strength thereof.
Two principal types of binders are used with glass blocks namely mortar and silicone caulking. In mortar, a relatively strong bond can be achieved, however the appearance of mortar joints in glass block walls differs markedly from the appearance of silicone joints, and so these types of binder have different appeal to different people.
Silicone can provide an aesthetically appealing joint between glass blocks, it being of a similar colour to glass or alternatively being able to be pigmented to any desirable colour, and is able to be used with smaller spaced joints so that the joints do not detract from the appearance of the glass blocks.
With both types of binder, expansion and contraction of the glass blocks with variations in temperature needs to be accommodated. This is a major problem where the glass block wall needs to connect to either a frame or a wall made of some other material which has a different rate of expansion or contraction. As glass is extremely fragile this expansion or contraction can result in cracking of the glass blocks themselves or the joints if this expansion and contraction is not accommodated. Consequently, the use of a modular framing system has become popular with the construction of glass block walls, wherein a glass block wall matrix is constructed within a rectangular frame of a predetermined size which allows for a void to be disposed between the interface of the periphery of the glass block wall and the inner surface of the frame itself along the jambs, the head and the sill of the frame. The void along the jambs may be occupied by a suitable flexible medium such as polystyrene foam to allow for the expansion and contraction of the glass blocks within the frame.
A series of these glass block wall frames can be constructed and interconnected to form a matrix of glass block wall frames which in turn form a composite wall of the appropriate size.
Notwithstanding the adoption of these types of framing systems for the laying of glass blocks, there is still a need to reinforce the joints due to the orthogonal bond required for the blocks. This is particularly so with the use of silicone as a binder which simply does not have the same inherent strength characteristics as mortar. Even with the increased strength characteristics of mortar, it is still necessary to use some kind of reinforcement when using this as a binder, particularly with external walls.
In the case of wall construction using mortar as a binder, 6 mm diameter galvanised steel rod has been used which is embedded within the mortar layer to reinforce the bonding. In the case of wall construction using silicone as a binder, it has been found necessary to use a stronger reinforcement such as galvanised flat bar of 50 mm.times.3 mm, which is positioned within the interstices of the joints by elaborate fixing methods.
Another problem with the laying of glass blocks is the need to achieve and maintain an orthogonal bond in order to ensure clean aesthetic appearance. Although the achievement of straight horizontal joints is relatively simple with most block laying techniques, be it brick laying or glass block laying, the achievement of straight and neat vertical joints is much more difficult. Consequently, the use of spacers to precisely space the blocks apart both horizontally and vertically has become standard practice throughout the industry to achieve clean, straight and consistent spacing between the blocks along the joints.
In order to accommodate both reinforcement and spacing requirements for glass block wall construction, the design of spacers has become quite involved.
With respect to glass block wall construction using mortar as a binder, the spacers are required to be quite thick and bulky to achieve glass block spacings of the standard 10 mm adopted for mortar joints, whereas with the use of silicone as a binder, the spacers are much thinner, requiring them to be more complex in design. The complexity of the design of spacers is due in part to accommodating reinforcement members and in part to the complex shape of the adjoining end faces of the glass blocks.
In this respect, a typical glass block comprises two parallel rectangular side faces which become the exposed faces of the block and four adjoining end faces which orthogonally adjoin the corresponding edges of the side faces. The ends of each of these side faces contiguously adjoin each other orthogonally to form a continuous circumferential edge of the block which is convexly curved at each of its corners. However, the profile of the circumferential edge is substantially concave whereby the corresponding edges of the side faces each define an outer cusp along the opposing sides of each end face as well as a central inner cusp which is disposed intermediate the opposing side faces of each end face. This inner cusp extends continuously along the circumferential edge of the block on each of the side faces of the block forming the same.
Due to the lesser reinforcement required with mortar joints, the design of spacers for glass block wall construction using this type of binder is relatively simple and consequently a variety of spacers are available on the market for this purpose. One of the better types of spacers for this purpose is the subject of Australian Patent No 608220.
In the case of glass block wall construction which uses silicone as a binder, due to the decreased spacing requirements of the blocks, typically being in the order of 3 mm and the increased reinforcement required, the design of spacers has been much more complex. Two systems which are most commonly used in the trade in Australia are the subject of Australian Patent No 637665 and Australian Patent Specification No 29361/89 respectively. Both of these systems, whilst becoming popular, still have considerable disadvantages associated therewith.
In the case of Australian Patent No 637665, the spacer and reinforcement member are one and the same, in this case, being a member formed of a flexible plastics material such as flexible polyvinyl chloride. This member is dispensed in prescribed lengths which span the entire horizontal joint, being cut from a large roll of the same. Unfortunately, due to the flexible nature of the spacer material, the reinforcement is not as strong as can be achieved by the use of metal reinforcement bars and so the utility of this type of glass block wall construction is limited principally to internal walls, where the lateral loading requirements are not as critical as with external walls. Furthermore, discrete lengths of the member are cut and disposed between the blocks to form the vertical spacing. The discrete nature of the vertical spacers however provides no additional strength characteristics and so these members function solely as a spacer and not as reinforcement.
In the case of Australian Patent Specification No 29361/89, which describes what is commonly known as the "Steckfix" (trade mark) system , this system overcomes the loading limitation of the previous system to a significant degree by utilising a flat metal bar as the reinforcing member and discrete plastic spacers which are connected to the bar for the spacing requirements. The inherent strength of the flat metal bar significantly improves the loading characteristics of glass block walls constructed in accordance with this system and hence such walls can be used both internally and externally. A problem with this system, however is that the spacers which connect to the flat metal bar allow for spacing in only one direction.
In the case of the flat metal bars being disposed horizontally, the spacer which is connected to the bar is only capable of spacing the horizontal joints and hence a discrete spacer is required to provide the spacing for the vertical joints. Conversely, if the bars are disposed vertically, discrete spacers are required to provide for the spacing of the horizontal joints. Again, as these discrete spacers are separate from the spacers which are connected to the reinforcing metal bar, they do not contribute at all to the loading characteristics of the wall.
Another disadvantage of this system is that only one side of the spacer conforms to the complex shape of the end face profile of the glass block, the other side of the spacer by virtue of accommodating the flat bar, does not conform to the complex shape of thee end face profile. Hence the maximum strength that could otherwise be obtained from the bar if it was to more positively engage the confronting faces of both adjacent blocks, is not achieved.